Zur Kenntnis des Lignins (15. Mitteil.)

Freudenberg, Karl; Janson, Alfons; Knopf, Erich; Haag, Alfred

doi:10.1002/cber.19360690637

Cited by 47 publications

(7 citation statements)

References 9 publications

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“…The analytical procedure used in these studies, known as permanganate oxidation, follows a protocol adopted from earlier work by Freudenberg (Freudenberg et al, 1936), and later by Larsson and Miksche (1967), and that relies on the treatment of lignin (isolated from, or embedded in pulp fibers) with diethylsulfate, an effective ethylating agent for phenolic hydroxyl groups; subsequent oxidative hydrolysis with alkaline cupric oxide; followed by methylation with dimethylsufate; and oxidation of non-aromatic lignin entities with permanganate and hydrogen peroxide (Morohoshi and Glasser, 1979). The resulting mixture of aromatic carboxylic acids is quantitatively separated by gas and gel chromatography following esterification with diazomethane.…”

Section: Structural Aspectsmentioning

confidence: 99%

About Making Lignin Great Again—Some Lessons From the Past

2019

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Lignin, the second most abundant biopolymer on the planet, serves land-plants as bonding agent in juvenile cell tissues and as stiffening (modulus-building) agent in mature cell walls. The chemical structure analysis of cell wall lignins from two partially delignified wood species representing between 6 and 65% of total wood lignin has revealed that cell wall-bound lignins are virtually invariable in terms of inter-unit linkages, and resemble the native state. Variability is recognized as the result of isolation procedure. In native state, lignin has a low glass-to-rubber transition temperature and is part of a block copolymer with non-crystalline polysaccharides. This molecular architecture determines all of lignin's properties, foremost of all its failure to undergo interfacial failure by separation from (semi-) crystalline cellulose under a wide range of environmental conditions. This seemingly unexpected compatibility (on the nano-level) between a carbohydrate component and the highly aromatic lignin represents a lesson by nature that human technology is only now beginning to mimic. Since the isolation of lignin from lignocellulosic biomass (i.e., by pulping or biorefining) necessitates significant molecular alteration of lignin, isolated lignins are highly variable in structure and reflect the isolation method. While numerous procedures exist for converting isolated (carbon-rich) lignins into well-defined commodity chemicals by various liquefaction techniques (such as pyrolysis, hydrogenolysis, etc.), the use of lignin in man-made thermosetting and thermoplastic structural materials appears to offer greatest value. The well-recognized variabilities of isolated lignins can in large part be remedied by targeted chemical modification, and by adopting nature's principles of functionalization leading to inter-molecular compatibility. Lignins isolated from large-scale industrial delignification processes operating under invariable isolation conditions produce polymers of virtually invariable character. This makes lignin from pulp mills a potentially valuable biopolymeric resource. The restoration of molecular character resembling that in native plants is illustrated in this review via the demonstrated (and in part commercially-implemented) use of pulp lignins in bio-degradable (or compostable) polymeric materials.

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Section: Structural Aspectsmentioning

confidence: 99%

About Making Lignin Great Again—Some Lessons From the Past

2019

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“…The difficultly hydrolyzable poly saccharides, including cellulose, are then dissolved from the loosened structure through application of a solution of copper oxide in am monia. A part of the less polymerized forms of lignin which are linked to sugar can be removed previous to either of the above-men tioned treatments by cold alkali or by organic solvents such as cold formic acid (67). This treatment is of little importance for spruce as only small amounts of the wood are soluble.…”

Section: Isolationmentioning

confidence: 99%

“…Alkali.-Spruce lignin (67,84), or better the wood itself, subse quent to methylation with diazomethane, 90 minutes cooking with 70 per cent potassium hydroxide at 165 to 1700, methylation with dimethylsulphate, and oxidation with permanganate yields (calculated from lignin content) : 20 to 21 per cent veratric acid (XXIV), 6 to 12 per cent isohemipinic acid (XXV), 2 to 3 per cent dehydrodiveratric acid (XXVI), and traces of trimethylgallic acid.…”

Section: Degradation Following Cleavage Of Ether Bondsmentioning

confidence: 99%

Polysaccharides and Lignin

Freudenberg

1939

Annu. Rev. Biochem.

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“…Because efficient fabrication of high quality pulps is necessary for delignification in not only woods but also in unbleached pulps, many methods with regard to delignification have been proposed, including chemical oxidations using chlorine dioxide (Rajan et al 1994), oxygen (Kratzl et al 1966), KMnO 4 (Freudenberg et al 1936), fungi (Hirai et al 1994), and enzymes, e.g., manganese peroxidase (Jensen et al 1996). It is also considered that the efficient ruptures of the ether bond, e.g., b-O-4 and/or a-O-4 bonds in wood lignins are necessary not only to produce the high quality pulp but also to decrease the amount of the chlorinated compounds which are generated by the products in the chlorine bleaching pulping process and are the source of toxic compounds, e.g., dioxins (Uraki et al 1997).…”

Section: Introductionmentioning

confidence: 99%

Homolytic Scission of Interunitary Bonds in Lignin Induced by Ultrasonic Irradiation of MWL Dissolved in Dimethylsulfoxide

Yoshioka¹,

Seino²,

Tabata³

et al. 2000

Holzforschung

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An electron spin resonance (ESR) method combined with a spin trapping technique was applied to trap and characterize unstable radicals which were generated by ultrasonic irradiation of the dimethylsulfoxide (DMSO) solution of a softwood, Yezo Spruce (Picea jezoensis carr.) lignin. It was found that an unstable secondary carbon radical,~CH • in the solution was trapped as the stable nitroxide spin adduct when the DMSO solution was subjected to ultrasonic irradiation in the presence of a spin trapping reagent: 2,4,6-tri-tert-butylnitrosobenzene (BNB) at 50°C for 30 min. This means that the alkyl phenyl ether bonds,~CH-O-phenyl, known as interunitary bonds in lignins were homolytically cleaved by the ultrasonic irradiation, although the phenoxy radical Ph-O •, called guaiacoxy radical, i.e. the counter radical of the secondary carbon radical, was not trapped by the BNB spin trap. This suggests that the trapping of the guaiacoxy radical, having a methoxy group in an ortho-position, by the BNB molecule, carrying two bulky butyl groups in the ortho-positions, is sterically hindered. KeywordsYezo spruce (Picea jezoensis carr.) Milled wood lignin (MWL) Electron spin resonance (ESR) Spin trapping Phenoxy radicals Alkyl phenyl ether bonds Secondary carbon radical Ultrasonic irradiation Brought to you by | University of Queensland -UQ Library Authenticated Download Date | 6/23/15 7:21 AM

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Zur Kenntnis des Lignins (15. Mitteil.)

Cited by 47 publications

References 9 publications

About Making Lignin Great Again—Some Lessons From the Past

About Making Lignin Great Again—Some Lessons From the Past

Polysaccharides and Lignin

Homolytic Scission of Interunitary Bonds in Lignin Induced by Ultrasonic Irradiation of MWL Dissolved in Dimethylsulfoxide

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